[PATCH 00/11] mm: thp: always enable mTHP support

[PATCH 00/11] mm: thp: always enable mTHP support

[Luiz Capitulino]

Today, if an architecture implements has_transparent_hugepage() and the CPU
lacks support for PMD-sized pages, the THP code disables all THP, including
mTHP. In addition, the kernel lacks a well defined API to check for
PMD-sized page support. It currently relies on has_transparent_hugepage()
and thp_disabled_by_hw(), but they are not well defined and are tied to
THP support.

This series addresses both issues by introducing a new well defined API
to query PMD-sized page support: pgtable_has_pmd_leaves(). Using this
new helper, we ensure that mTHP remains enabled even when the
architecture or CPU doesn't support PMD-sized pages.

Please, note that we need to do the same refactoring for
has_transparent_pud_hugepage(). I actually have patches for this one too,
I'm planning to post it as a follow up to this series in the near future.

Thanks to David Hildenbrand for suggesting this improvement and for
providing guidance (all bugs and misconcentpions are mine).

This is on top of latest mm-new branch commit d0a24447990a ("mm/hugetlb:
fix excessive IPI broadcasts when unsharing PMD tables using mmu_gather").

v1
--
- Call init_arch_has_pmd_leaves() from start_kernel()
- Keep pgtable_has_pmd_leaves() calls tied to CONFIG_TRANSPARENT_HUGEPAGE (David)
- Clear PUD_ORDER when clearing PMD_ORDER (David)
- Small changelog improvements (David)
- Rebased on top of latest mm-new

Luiz Capitulino (11):
  docs: tmpfs: remove implementation detail reference
  mm: introduce pgtable_has_pmd_leaves()
  drivers: dax: use pgtable_has_pmd_leaves()
  drivers: i915 selftest: use pgtable_has_pmd_leaves()
  drivers: nvdimm: use pgtable_has_pmd_leaves()
  mm: debug_vm_pgtable: use pgtable_has_pmd_leaves()
  mm: shmem: use pgtable_has_pmd_leaves()
  treewide: rename has_transparent_hugepage() to arch_has_pmd_leaves()
  mm: replace thp_disabled_by_hw() with pgtable_has_pmd_leaves()
  mm/thp: always enable mTHP support
  mm/thp: x86: cleanup PSE feature bit usage

 Documentation/filesystems/tmpfs.rst           |  5 ++---
 arch/mips/include/asm/pgtable.h               |  4 ++--
 arch/mips/mm/tlb-r4k.c                        |  4 ++--
 arch/powerpc/include/asm/book3s/64/hash-4k.h  |  2 +-
 arch/powerpc/include/asm/book3s/64/hash-64k.h |  2 +-
 arch/powerpc/include/asm/book3s/64/pgtable.h  | 10 +++++-----
 arch/powerpc/include/asm/book3s/64/radix.h    |  2 +-
 arch/powerpc/mm/book3s64/hash_pgtable.c       |  4 ++--
 arch/s390/include/asm/pgtable.h               |  4 ++--
 arch/x86/include/asm/pgtable.h                |  6 ------
 arch/x86/include/asm/pgtable_32.h             |  6 ++++++
 drivers/dax/dax-private.h                     |  2 +-
 .../gpu/drm/i915/gem/selftests/huge_pages.c   |  4 +++-
 drivers/nvdimm/pfn_devs.c                     |  6 ++++--
 include/linux/huge_mm.h                       |  7 -------
 include/linux/pgtable.h                       | 11 ++++++++--
 init/main.c                                   |  1 +
 mm/debug_vm_pgtable.c                         | 20 +++++++++----------
 mm/huge_memory.c                              | 13 ++++++------
 mm/memory.c                                   | 10 +++++++++-
 mm/shmem.c                                    |  9 +++++----
 21 files changed, 73 insertions(+), 59 deletions(-)

-- 
2.52.0

[PATCH 01/11] docs: tmpfs: remove implementation detail reference

[Luiz Capitulino]

The tmpfs.rst doc references the has_transparent_hugepage() helper, which
is an implementation detail in the kernel and not relevant for users
wishing to properly configure THP support for tmpfs. Remove it.

Acked-by: David Hildenbrand (Red Hat) <david@kernel.org>
Signed-off-by: Luiz Capitulino <luizcap@redhat.com>
---
 Documentation/filesystems/tmpfs.rst | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/Documentation/filesystems/tmpfs.rst b/Documentation/filesystems/tmpfs.rst
index d677e0428c3f..46fc986c3388 100644
--- a/Documentation/filesystems/tmpfs.rst
+++ b/Documentation/filesystems/tmpfs.rst
@@ -109,9 +109,8 @@ noswap  Disables swap. Remounts must respect the original settings.
 ======  ===========================================================
 
 tmpfs also supports Transparent Huge Pages which requires a kernel
-configured with CONFIG_TRANSPARENT_HUGEPAGE and with huge supported for
-your system (has_transparent_hugepage(), which is architecture specific).
-The mount options for this are:
+configured with CONFIG_TRANSPARENT_HUGEPAGE and with huge pages
+supported for your system. The mount options for this are:
 
 ================ ==============================================================
 huge=never       Do not allocate huge pages.  This is the default.
-- 
2.52.0

[PATCH 02/11] mm: introduce pgtable_has_pmd_leaves()

[Luiz Capitulino]

Currently, we have two helpers that check for PMD-sized pages but have
different names and slightly different semantics:

- has_transparent_hugepages(): the name suggests it checks if THP is
  enabled, but it actually checks if the CPU supports PMD-sized pages.
  It may perform a hardware check, so it can't be used in fast paths

- thp_disabled_by_hw(): the name suggests it checks if THP is disabled
  by the hardware, but it just returns a cached value acquired with
  has_transparent_hugepages(). This way, this helper can be called from
  fast paths

This commit introduces a new helper called pgtable_has_pmd_leaves()
which is intended to replace both has_transparent_hugepages() and
thp_disable_by_hw(). pgtable_has_pmd_leaves() has very clear semantics:
it returns true if the CPU supports PMD-sized pages and false otherwise.
It always returns a cached value, so it can be used in fast paths.

The new helper requires an initialization step that needs to be
performed very early during boot because there are
pgtable_has_pmd_leaves() users that want to call it from __setup()
handlers. This initialization is performed by init_arch_has_pmd_leaves(),
called early from start_kernel().

The next commits will convert users of both has_transparent_hugepages()
and thp_disabled_by_hw() to pgtable_has_pmd_leaves().

Signed-off-by: Luiz Capitulino <luizcap@redhat.com>
---
 include/linux/pgtable.h | 7 +++++++
 init/main.c             | 1 +
 mm/memory.c             | 8 ++++++++
 3 files changed, 16 insertions(+)

diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 652f287c1ef6..6733f90a1da4 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -2017,6 +2017,13 @@ static inline const char *pgtable_level_to_str(enum pgtable_level level)
 	}
 }
 
+extern bool __arch_has_pmd_leaves;
+static inline bool pgtable_has_pmd_leaves(void)
+{
+	return __arch_has_pmd_leaves;
+}
+void __init init_arch_has_pmd_leaves(void);
+
 #endif /* !__ASSEMBLY__ */
 
 #if !defined(MAX_POSSIBLE_PHYSMEM_BITS) && !defined(CONFIG_64BIT)
diff --git a/init/main.c b/init/main.c
index b84818ad9685..ad1209fffcde 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1036,6 +1036,7 @@ void start_kernel(void)
 	smp_prepare_boot_cpu();	/* arch-specific boot-cpu hooks */
 	early_numa_node_init();
 	boot_cpu_hotplug_init();
+	init_arch_has_pmd_leaves();
 
 	print_kernel_cmdline(saved_command_line);
 	/* parameters may set static keys */
diff --git a/mm/memory.c b/mm/memory.c
index 2a55edc48a65..79bd59d5243f 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -177,6 +177,14 @@ static int __init init_zero_pfn(void)
 }
 early_initcall(init_zero_pfn);
 
+bool __arch_has_pmd_leaves __read_mostly;
+EXPORT_SYMBOL(__arch_has_pmd_leaves);
+
+void __init init_arch_has_pmd_leaves(void)
+{
+	__arch_has_pmd_leaves = has_transparent_hugepage();
+}
+
 void mm_trace_rss_stat(struct mm_struct *mm, int member)
 {
 	trace_rss_stat(mm, member);
-- 
2.52.0

[PATCH 03/11] drivers: dax: use pgtable_has_pmd_leaves()

[Luiz Capitulino]

dax_align_valid() uses has_transparent_hugepage() to check if PMD-sized
pages are supported, use pgtable_has_pmd_leaves() instead.

Acked-by: David Hildenbrand (Red Hat) <david@kernel.org>
Signed-off-by: Luiz Capitulino <luizcap@redhat.com>
---
 drivers/dax/dax-private.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/dax/dax-private.h b/drivers/dax/dax-private.h
index 0867115aeef2..10aeaec9e789 100644
--- a/drivers/dax/dax-private.h
+++ b/drivers/dax/dax-private.h
@@ -117,7 +117,7 @@ static inline bool dax_align_valid(unsigned long align)
 {
 	if (align == PUD_SIZE && IS_ENABLED(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD))
 		return true;
-	if (align == PMD_SIZE && has_transparent_hugepage())
+	if (align == PMD_SIZE && pgtable_has_pmd_leaves())
 		return true;
 	if (align == PAGE_SIZE)
 		return true;
-- 
2.52.0

[PATCH 04/11] drivers: i915 selftest: use pgtable_has_pmd_leaves()

[Luiz Capitulino]

igt_can_allocate_thp() uses has_transparent_hugepage() to check if
PMD-sized pages are supported, use pgtable_has_pmd_leaves() instead.

Since igt_can_allocate_thp() wants to use PMD-sized pages with THP,
also check if THP is built-in with IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE).

Signed-off-by: Luiz Capitulino <luizcap@redhat.com>
---
 drivers/gpu/drm/i915/gem/selftests/huge_pages.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
index bd08605a1611..dcd1f1141513 100644
--- a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
+++ b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
@@ -1316,7 +1316,9 @@ typedef struct drm_i915_gem_object *
 
 static inline bool igt_can_allocate_thp(struct drm_i915_private *i915)
 {
-	return i915->mm.gemfs && has_transparent_hugepage();
+	return i915->mm.gemfs &&
+		IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
+		pgtable_has_pmd_leaves();
 }
 
 static struct drm_i915_gem_object *
-- 
2.52.0

[PATCH 05/11] drivers: nvdimm: use pgtable_has_pmd_leaves()

[Luiz Capitulino]

nd_pfn_supported_alignments() and nd_pfn_default_alignment() use
has_transparent_hugepage() to check if PMD-sized pages are supported,
use pgtable_has_pmd_leaves() instead.

Since both functions want to use PMD-sized pages with THP, also check if
THP is built-in with IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE).

Signed-off-by: Luiz Capitulino <luizcap@redhat.com>
---
 drivers/nvdimm/pfn_devs.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c
index 42b172fc5576..7ee8ec50e72d 100644
--- a/drivers/nvdimm/pfn_devs.c
+++ b/drivers/nvdimm/pfn_devs.c
@@ -94,7 +94,8 @@ static unsigned long *nd_pfn_supported_alignments(unsigned long *alignments)
 
 	alignments[0] = PAGE_SIZE;
 
-	if (has_transparent_hugepage()) {
+	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
+	    pgtable_has_pmd_leaves()) {
 		alignments[1] = HPAGE_PMD_SIZE;
 		if (has_transparent_pud_hugepage())
 			alignments[2] = HPAGE_PUD_SIZE;
@@ -109,7 +110,8 @@ static unsigned long *nd_pfn_supported_alignments(unsigned long *alignments)
 static unsigned long nd_pfn_default_alignment(void)
 {
 
-	if (has_transparent_hugepage())
+	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
+	    pgtable_has_pmd_leaves())
 		return HPAGE_PMD_SIZE;
 	return PAGE_SIZE;
 }
-- 
2.52.0

[PATCH 06/11] mm: debug_vm_pgtable: use pgtable_has_pmd_leaves()

[Luiz Capitulino]

debug_vm_pgtable calls has_transparent_hugepage() in multiple places to
check if PMD-sized pages are supported, use pgtable_has_pmd_leaves()
instead.

Signed-off-by: Luiz Capitulino <luizcap@redhat.com>
---
 mm/debug_vm_pgtable.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index ae9b9310d96f..ec02bafd9d45 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -177,7 +177,7 @@ static void __init pmd_basic_tests(struct pgtable_debug_args *args, int idx)
 	unsigned long val = idx, *ptr = &val;
 	pmd_t pmd;
 
-	if (!has_transparent_hugepage())
+	if (!pgtable_has_pmd_leaves())
 		return;
 
 	pr_debug("Validating PMD basic (%pGv)\n", ptr);
@@ -222,7 +222,7 @@ static void __init pmd_advanced_tests(struct pgtable_debug_args *args)
 	pmd_t pmd;
 	unsigned long vaddr = args->vaddr;
 
-	if (!has_transparent_hugepage())
+	if (!pgtable_has_pmd_leaves())
 		return;
 
 	page = (args->pmd_pfn != ULONG_MAX) ? pfn_to_page(args->pmd_pfn) : NULL;
@@ -283,7 +283,7 @@ static void __init pmd_leaf_tests(struct pgtable_debug_args *args)
 {
 	pmd_t pmd;
 
-	if (!has_transparent_hugepage())
+	if (!pgtable_has_pmd_leaves())
 		return;
 
 	pr_debug("Validating PMD leaf\n");
@@ -688,7 +688,7 @@ static void __init pmd_protnone_tests(struct pgtable_debug_args *args)
 	if (!IS_ENABLED(CONFIG_NUMA_BALANCING))
 		return;
 
-	if (!has_transparent_hugepage())
+	if (!pgtable_has_pmd_leaves())
 		return;
 
 	pr_debug("Validating PMD protnone\n");
@@ -737,7 +737,7 @@ static void __init pmd_soft_dirty_tests(struct pgtable_debug_args *args)
 	if (!pgtable_supports_soft_dirty())
 		return;
 
-	if (!has_transparent_hugepage())
+	if (!pgtable_has_pmd_leaves())
 		return;
 
 	pr_debug("Validating PMD soft dirty\n");
@@ -754,7 +754,7 @@ static void __init pmd_leaf_soft_dirty_tests(struct pgtable_debug_args *args)
 	    !IS_ENABLED(CONFIG_ARCH_ENABLE_THP_MIGRATION))
 		return;
 
-	if (!has_transparent_hugepage())
+	if (!pgtable_has_pmd_leaves())
 		return;
 
 	pr_debug("Validating PMD swap soft dirty\n");
@@ -825,7 +825,7 @@ static void __init pmd_softleaf_tests(struct pgtable_debug_args *args)
 	swp_entry_t arch_entry;
 	pmd_t pmd1, pmd2;
 
-	if (!has_transparent_hugepage())
+	if (!pgtable_has_pmd_leaves())
 		return;
 
 	pr_debug("Validating PMD swap\n");
@@ -906,7 +906,7 @@ static void __init pmd_thp_tests(struct pgtable_debug_args *args)
 {
 	pmd_t pmd;
 
-	if (!has_transparent_hugepage())
+	if (!pgtable_has_pmd_leaves())
 		return;
 
 	pr_debug("Validating PMD based THP\n");
@@ -993,7 +993,7 @@ static void __init destroy_args(struct pgtable_debug_args *args)
 	}
 
 	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
-	    has_transparent_hugepage() &&
+	    pgtable_has_pmd_leaves() &&
 	    args->pmd_pfn != ULONG_MAX) {
 		if (args->is_contiguous_page) {
 			free_contig_range(args->pmd_pfn, (1 << HPAGE_PMD_ORDER));
@@ -1253,7 +1253,7 @@ static int __init init_args(struct pgtable_debug_args *args)
 	}
 
 	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
-	    has_transparent_hugepage()) {
+	    pgtable_has_pmd_leaves()) {
 		page = debug_vm_pgtable_alloc_huge_page(args, HPAGE_PMD_ORDER);
 		if (page) {
 			args->pmd_pfn = page_to_pfn(page);
-- 
2.52.0

[PATCH 07/11] mm: shmem: use pgtable_has_pmd_leaves()

[Luiz Capitulino]

Shmem uses has_transparent_hugepage() to check if PMD-sized pages are
supported, use pgtable_has_pmd_leaves() instead.

Signed-off-by: Luiz Capitulino <luizcap@redhat.com>
---
 mm/shmem.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index b329b5302c48..ad5825667b49 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -689,7 +689,8 @@ static int shmem_parse_huge(const char *str)
 	else
 		return -EINVAL;
 
-	if (!has_transparent_hugepage() &&
+	if (!(IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
+	      pgtable_has_pmd_leaves()) &&
 	    huge != SHMEM_HUGE_NEVER && huge != SHMEM_HUGE_DENY)
 		return -EINVAL;
 
@@ -4655,7 +4656,7 @@ static int shmem_parse_one(struct fs_context *fc, struct fs_parameter *param)
 		ctx->huge = result.uint_32;
 		if (ctx->huge != SHMEM_HUGE_NEVER &&
 		    !(IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
-		      has_transparent_hugepage()))
+		      pgtable_has_pmd_leaves()))
 			goto unsupported_parameter;
 		ctx->seen |= SHMEM_SEEN_HUGE;
 		break;
@@ -5439,7 +5440,7 @@ void __init shmem_init(void)
 #endif
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-	if (has_transparent_hugepage() && shmem_huge > SHMEM_HUGE_DENY)
+	if (pgtable_has_pmd_leaves() && shmem_huge > SHMEM_HUGE_DENY)
 		SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
 	else
 		shmem_huge = SHMEM_HUGE_NEVER; /* just in case it was patched */
-- 
2.52.0

[PATCH 08/11] treewide: rename has_transparent_hugepage() to arch_has_pmd_leaves()

[Luiz Capitulino]

Now that all has_transparent_hugepage() callers have been converted to
pgtable_has_pmd_leaves(), rename has_transparent_hugepage() to
arch_has_pmd_leaves() since that's what the helper checks for.

arch_has_pmd_leaves() is supposed to be called only by
init_arch_has_pmd_leaves(). The only temporary exception is
hugepage_init() which will be converted in a future commit.

Signed-off-by: Luiz Capitulino <luizcap@redhat.com>
---
 arch/mips/include/asm/pgtable.h               |  4 ++--
 arch/mips/mm/tlb-r4k.c                        |  4 ++--
 arch/powerpc/include/asm/book3s/64/hash-4k.h  |  2 +-
 arch/powerpc/include/asm/book3s/64/hash-64k.h |  2 +-
 arch/powerpc/include/asm/book3s/64/pgtable.h  | 10 +++++-----
 arch/powerpc/include/asm/book3s/64/radix.h    |  2 +-
 arch/powerpc/mm/book3s64/hash_pgtable.c       |  4 ++--
 arch/s390/include/asm/pgtable.h               |  4 ++--
 arch/x86/include/asm/pgtable.h                |  4 ++--
 include/linux/pgtable.h                       |  4 ++--
 mm/huge_memory.c                              |  2 +-
 mm/memory.c                                   |  2 +-
 12 files changed, 22 insertions(+), 22 deletions(-)

diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
index 9c06a612d33a..0080724a7df5 100644
--- a/arch/mips/include/asm/pgtable.h
+++ b/arch/mips/include/asm/pgtable.h
@@ -615,8 +615,8 @@ unsigned long io_remap_pfn_range_pfn(unsigned long pfn, unsigned long size);
 /* We don't have hardware dirty/accessed bits, generic_pmdp_establish is fine.*/
 #define pmdp_establish generic_pmdp_establish
 
-#define has_transparent_hugepage has_transparent_hugepage
-extern int has_transparent_hugepage(void);
+#define arch_has_pmd_leaves arch_has_pmd_leaves
+extern int arch_has_pmd_leaves(void);
 
 static inline int pmd_trans_huge(pmd_t pmd)
 {
diff --git a/arch/mips/mm/tlb-r4k.c b/arch/mips/mm/tlb-r4k.c
index 44a662536148..4fcc8195a130 100644
--- a/arch/mips/mm/tlb-r4k.c
+++ b/arch/mips/mm/tlb-r4k.c
@@ -432,7 +432,7 @@ void add_wired_entry(unsigned long entrylo0, unsigned long entrylo1,
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 
-int has_transparent_hugepage(void)
+int arch_has_pmd_leaves(void)
 {
 	static unsigned int mask = -1;
 
@@ -448,7 +448,7 @@ int has_transparent_hugepage(void)
 	}
 	return mask == PM_HUGE_MASK;
 }
-EXPORT_SYMBOL(has_transparent_hugepage);
+EXPORT_SYMBOL(arch_has_pmd_leaves);
 
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE  */
 
diff --git a/arch/powerpc/include/asm/book3s/64/hash-4k.h b/arch/powerpc/include/asm/book3s/64/hash-4k.h
index 8e5bd9902bed..6744c2287199 100644
--- a/arch/powerpc/include/asm/book3s/64/hash-4k.h
+++ b/arch/powerpc/include/asm/book3s/64/hash-4k.h
@@ -165,7 +165,7 @@ extern void hash__pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
 extern pgtable_t hash__pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp);
 extern pmd_t hash__pmdp_huge_get_and_clear(struct mm_struct *mm,
 				       unsigned long addr, pmd_t *pmdp);
-extern int hash__has_transparent_hugepage(void);
+extern int hash__arch_has_pmd_leaves(void);
 #endif
 
 #endif /* !__ASSEMBLER__ */
diff --git a/arch/powerpc/include/asm/book3s/64/hash-64k.h b/arch/powerpc/include/asm/book3s/64/hash-64k.h
index 7deb3a66890b..9392aba5e5dc 100644
--- a/arch/powerpc/include/asm/book3s/64/hash-64k.h
+++ b/arch/powerpc/include/asm/book3s/64/hash-64k.h
@@ -278,7 +278,7 @@ extern void hash__pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
 extern pgtable_t hash__pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp);
 extern pmd_t hash__pmdp_huge_get_and_clear(struct mm_struct *mm,
 				       unsigned long addr, pmd_t *pmdp);
-extern int hash__has_transparent_hugepage(void);
+extern int hash__arch_has_pmd_leaves(void);
 #endif /*  CONFIG_TRANSPARENT_HUGEPAGE */
 
 #endif	/* __ASSEMBLER__ */
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index aac8ce30cd3b..6ed036b3d3c2 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -1094,14 +1094,14 @@ static inline void update_mmu_cache_pud(struct vm_area_struct *vma,
 {
 }
 
-extern int hash__has_transparent_hugepage(void);
-static inline int has_transparent_hugepage(void)
+extern int hash__arch_has_pmd_leaves(void);
+static inline int arch_has_pmd_leaves(void)
 {
 	if (radix_enabled())
-		return radix__has_transparent_hugepage();
-	return hash__has_transparent_hugepage();
+		return radix__arch_has_pmd_leaves();
+	return hash__arch_has_pmd_leaves();
 }
-#define has_transparent_hugepage has_transparent_hugepage
+#define arch_has_pmd_leaves arch_has_pmd_leaves
 
 static inline int has_transparent_pud_hugepage(void)
 {
diff --git a/arch/powerpc/include/asm/book3s/64/radix.h b/arch/powerpc/include/asm/book3s/64/radix.h
index da954e779744..c884a119cbd9 100644
--- a/arch/powerpc/include/asm/book3s/64/radix.h
+++ b/arch/powerpc/include/asm/book3s/64/radix.h
@@ -298,7 +298,7 @@ extern pmd_t radix__pmdp_huge_get_and_clear(struct mm_struct *mm,
 pud_t radix__pudp_huge_get_and_clear(struct mm_struct *mm,
 				     unsigned long addr, pud_t *pudp);
 
-static inline int radix__has_transparent_hugepage(void)
+static inline int radix__arch_has_pmd_leaves(void)
 {
 	/* For radix 2M at PMD level means thp */
 	if (mmu_psize_defs[MMU_PAGE_2M].shift == PMD_SHIFT)
diff --git a/arch/powerpc/mm/book3s64/hash_pgtable.c b/arch/powerpc/mm/book3s64/hash_pgtable.c
index 82d31177630b..1dec64bf0c75 100644
--- a/arch/powerpc/mm/book3s64/hash_pgtable.c
+++ b/arch/powerpc/mm/book3s64/hash_pgtable.c
@@ -366,7 +366,7 @@ pmd_t hash__pmdp_huge_get_and_clear(struct mm_struct *mm,
 	return old_pmd;
 }
 
-int hash__has_transparent_hugepage(void)
+int hash__arch_has_pmd_leaves(void)
 {
 
 	if (!mmu_has_feature(MMU_FTR_16M_PAGE))
@@ -395,7 +395,7 @@ int hash__has_transparent_hugepage(void)
 
 	return 1;
 }
-EXPORT_SYMBOL_GPL(hash__has_transparent_hugepage);
+EXPORT_SYMBOL_GPL(hash__arch_has_pmd_leaves);
 
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index bca9b29778c3..4398855d558e 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -1866,8 +1866,8 @@ static inline int pmd_trans_huge(pmd_t pmd)
 	return pmd_leaf(pmd);
 }
 
-#define has_transparent_hugepage has_transparent_hugepage
-static inline int has_transparent_hugepage(void)
+#define arch_has_pmd_leaves arch_has_pmd_leaves
+static inline int arch_has_pmd_leaves(void)
 {
 	return cpu_has_edat1() ? 1 : 0;
 }
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index e33df3da6980..08d109280e36 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -313,8 +313,8 @@ static inline int pud_trans_huge(pud_t pud)
 }
 #endif
 
-#define has_transparent_hugepage has_transparent_hugepage
-static inline int has_transparent_hugepage(void)
+#define arch_has_pmd_leaves arch_has_pmd_leaves
+static inline int arch_has_pmd_leaves(void)
 {
 	return boot_cpu_has(X86_FEATURE_PSE);
 }
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 6733f90a1da4..b4d10ea9e45a 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -2039,8 +2039,8 @@ void __init init_arch_has_pmd_leaves(void);
 #endif
 #endif
 
-#ifndef has_transparent_hugepage
-#define has_transparent_hugepage() IS_BUILTIN(CONFIG_TRANSPARENT_HUGEPAGE)
+#ifndef arch_has_pmd_leaves
+#define arch_has_pmd_leaves() IS_BUILTIN(CONFIG_TRANSPARENT_HUGEPAGE)
 #endif
 
 #ifndef has_transparent_pud_hugepage
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 40cf59301c21..b80a897b9b6f 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -905,7 +905,7 @@ static int __init hugepage_init(void)
 	int err;
 	struct kobject *hugepage_kobj;
 
-	if (!has_transparent_hugepage()) {
+	if (!arch_has_pmd_leaves()) {
 		transparent_hugepage_flags = 1 << TRANSPARENT_HUGEPAGE_UNSUPPORTED;
 		return -EINVAL;
 	}
diff --git a/mm/memory.c b/mm/memory.c
index 79bd59d5243f..e816d4b53bc0 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -182,7 +182,7 @@ EXPORT_SYMBOL(__arch_has_pmd_leaves);
 
 void __init init_arch_has_pmd_leaves(void)
 {
-	__arch_has_pmd_leaves = has_transparent_hugepage();
+	__arch_has_pmd_leaves = arch_has_pmd_leaves();
 }
 
 void mm_trace_rss_stat(struct mm_struct *mm, int member)
-- 
2.52.0

[PATCH 09/11] mm: replace thp_disabled_by_hw() with pgtable_has_pmd_leaves()

[Luiz Capitulino]

Despite its name, thp_disabled_by_hw() only checks whether the
architecture supports PMD-sized pages. It returns true when
TRANSPARENT_HUGEPAGE_UNSUPPORTED is set, which occurs if the
architecture implements arch_has_pmd_leaves() and that function
returns false.

Since pgtable_has_pmd_leaves() provides the same semantics, use it
instead.

Signed-off-by: Luiz Capitulino <luizcap@redhat.com>
---
 include/linux/huge_mm.h | 7 -------
 mm/huge_memory.c        | 6 ++----
 mm/memory.c             | 2 +-
 mm/shmem.c              | 2 +-
 4 files changed, 4 insertions(+), 13 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index a4d9f964dfde..e291a650b10f 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -47,7 +47,6 @@ vm_fault_t vmf_insert_folio_pud(struct vm_fault *vmf, struct folio *folio,
 				bool write);
 
 enum transparent_hugepage_flag {
-	TRANSPARENT_HUGEPAGE_UNSUPPORTED,
 	TRANSPARENT_HUGEPAGE_FLAG,
 	TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 	TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
@@ -352,12 +351,6 @@ static inline bool vma_thp_disabled(struct vm_area_struct *vma,
 	return mm_flags_test(MMF_DISABLE_THP_EXCEPT_ADVISED, vma->vm_mm);
 }
 
-static inline bool thp_disabled_by_hw(void)
-{
-	/* If the hardware/firmware marked hugepage support disabled. */
-	return transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_UNSUPPORTED);
-}
-
 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
 		unsigned long len, unsigned long pgoff, unsigned long flags);
 unsigned long thp_get_unmapped_area_vmflags(struct file *filp, unsigned long addr,
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index b80a897b9b6f..1e5ea2e47f79 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -122,7 +122,7 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma,
 	if (!vma->vm_mm)		/* vdso */
 		return 0;
 
-	if (thp_disabled_by_hw() || vma_thp_disabled(vma, vm_flags, forced_collapse))
+	if (!pgtable_has_pmd_leaves() || vma_thp_disabled(vma, vm_flags, forced_collapse))
 		return 0;
 
 	/* khugepaged doesn't collapse DAX vma, but page fault is fine. */
@@ -905,10 +905,8 @@ static int __init hugepage_init(void)
 	int err;
 	struct kobject *hugepage_kobj;
 
-	if (!arch_has_pmd_leaves()) {
-		transparent_hugepage_flags = 1 << TRANSPARENT_HUGEPAGE_UNSUPPORTED;
+	if (!pgtable_has_pmd_leaves())
 		return -EINVAL;
-	}
 
 	/*
 	 * hugepages can't be allocated by the buddy allocator
diff --git a/mm/memory.c b/mm/memory.c
index e816d4b53bc0..c35df4c477c1 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5383,7 +5383,7 @@ vm_fault_t do_set_pmd(struct vm_fault *vmf, struct folio *folio, struct page *pa
 	 * PMD mappings if THPs are disabled. As we already have a THP,
 	 * behave as if we are forcing a collapse.
 	 */
-	if (thp_disabled_by_hw() || vma_thp_disabled(vma, vma->vm_flags,
+	if (!pgtable_has_pmd_leaves() || vma_thp_disabled(vma, vma->vm_flags,
 						     /* forced_collapse=*/ true))
 		return ret;
 
diff --git a/mm/shmem.c b/mm/shmem.c
index ad5825667b49..6b350e336f8c 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1800,7 +1800,7 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode,
 	vm_flags_t vm_flags = vma ? vma->vm_flags : 0;
 	unsigned int global_orders;
 
-	if (thp_disabled_by_hw() || (vma && vma_thp_disabled(vma, vm_flags, shmem_huge_force)))
+	if (!pgtable_has_pmd_leaves() || (vma && vma_thp_disabled(vma, vm_flags, shmem_huge_force)))
 		return 0;
 
 	global_orders = shmem_huge_global_enabled(inode, index, write_end,
-- 
2.52.0

[PATCH 10/11] mm/thp: always enable mTHP support

[Luiz Capitulino]

If PMD-sized pages are not supported on an architecture (ie. the
arch implements arch_has_pmd_leaves() and it returns false) then the
current code disables all THP, including mTHP.

This commit fixes this by allowing mTHP to be always enabled for all
archs. When PMD-sized pages are not supported, its sysfs entry won't be
created and their mapping will be disallowed at page-fault time.

Signed-off-by: Luiz Capitulino <luizcap@redhat.com>
---
 mm/huge_memory.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 1e5ea2e47f79..882331592928 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -115,6 +115,9 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma,
 	else
 		supported_orders = THP_ORDERS_ALL_FILE_DEFAULT;
 
+	if (!pgtable_has_pmd_leaves())
+		supported_orders &= ~(BIT(PMD_ORDER) | BIT(PUD_ORDER));
+
 	orders &= supported_orders;
 	if (!orders)
 		return 0;
@@ -122,7 +125,7 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma,
 	if (!vma->vm_mm)		/* vdso */
 		return 0;
 
-	if (!pgtable_has_pmd_leaves() || vma_thp_disabled(vma, vm_flags, forced_collapse))
+	if (vma_thp_disabled(vma, vm_flags, forced_collapse))
 		return 0;
 
 	/* khugepaged doesn't collapse DAX vma, but page fault is fine. */
@@ -806,6 +809,9 @@ static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
 	}
 
 	orders = THP_ORDERS_ALL_ANON | THP_ORDERS_ALL_FILE_DEFAULT;
+	if (!pgtable_has_pmd_leaves())
+		orders &= ~(BIT(PMD_ORDER) | BIT(PUD_ORDER));
+
 	order = highest_order(orders);
 	while (orders) {
 		thpsize = thpsize_create(order, *hugepage_kobj);
@@ -905,9 +911,6 @@ static int __init hugepage_init(void)
 	int err;
 	struct kobject *hugepage_kobj;
 
-	if (!pgtable_has_pmd_leaves())
-		return -EINVAL;
-
 	/*
 	 * hugepages can't be allocated by the buddy allocator
 	 */
-- 
2.52.0

[PATCH 11/11] mm/thp: x86: cleanup PSE feature bit usage

[Luiz Capitulino]

Historically, THP support on x86 checked the PSE feature bit to enable
THP. On 64-bit, this check is redundant since PSE is always enabled by
default for compatibility. On 32-bit, PSE can enable 2 MiB or 4 MiB
page sizes so it must be checked. To clean this up, this commit:

1. Drops arch_has_pmd_leaves() from common x86 code. For 64-bit,
   we assume PMD-sized pages are always supported

2. Checks for PSE only on 32-bit by implementing arch_has_pmd_leaves()

Signed-off-by: Luiz Capitulino <luizcap@redhat.com>
---
 arch/x86/include/asm/pgtable.h    | 6 ------
 arch/x86/include/asm/pgtable_32.h | 6 ++++++
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 08d109280e36..55b88de5178f 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -313,12 +313,6 @@ static inline int pud_trans_huge(pud_t pud)
 }
 #endif
 
-#define arch_has_pmd_leaves arch_has_pmd_leaves
-static inline int arch_has_pmd_leaves(void)
-{
-	return boot_cpu_has(X86_FEATURE_PSE);
-}
-
 #ifdef CONFIG_ARCH_SUPPORTS_PMD_PFNMAP
 static inline bool pmd_special(pmd_t pmd)
 {
diff --git a/arch/x86/include/asm/pgtable_32.h b/arch/x86/include/asm/pgtable_32.h
index b612cc57a4d3..3bd51cfa431e 100644
--- a/arch/x86/include/asm/pgtable_32.h
+++ b/arch/x86/include/asm/pgtable_32.h
@@ -45,6 +45,12 @@ do {						\
 	flush_tlb_one_kernel((vaddr));		\
 } while (0)
 
+#define arch_has_pmd_leaves arch_has_pmd_leaves
+static inline int arch_has_pmd_leaves(void)
+{
+	return boot_cpu_has(X86_FEATURE_PSE);
+}
+
 #endif /* !__ASSEMBLER__ */
 
 /*
-- 
2.52.0

Re: [PATCH 01/11] docs: tmpfs: remove implementation detail reference

[Baolin Wang]

On 2025/12/16 05:16, Luiz Capitulino wrote:
> The tmpfs.rst doc references the has_transparent_hugepage() helper, which
> is an implementation detail in the kernel and not relevant for users
> wishing to properly configure THP support for tmpfs. Remove it.
> 
> Acked-by: David Hildenbrand (Red Hat) <david@kernel.org>
> Signed-off-by: Luiz Capitulino <luizcap@redhat.com>
> ---

Make sense to me.
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>

Re: [PATCH 07/11] mm: shmem: use pgtable_has_pmd_leaves()

[Baolin Wang]

On 2025/12/16 05:16, Luiz Capitulino wrote:
> Shmem uses has_transparent_hugepage() to check if PMD-sized pages are
> supported, use pgtable_has_pmd_leaves() instead.
> 
> Signed-off-by: Luiz Capitulino <luizcap@redhat.com>
> ---
>   mm/shmem.c | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/shmem.c b/mm/shmem.c
> index b329b5302c48..ad5825667b49 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -689,7 +689,8 @@ static int shmem_parse_huge(const char *str)
>   	else
>   		return -EINVAL;
>   
> -	if (!has_transparent_hugepage() &&
> +	if (!(IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
> +	      pgtable_has_pmd_leaves()) &&
>   	    huge != SHMEM_HUGE_NEVER && huge != SHMEM_HUGE_DENY)
>   		return -EINVAL;
>   
> @@ -4655,7 +4656,7 @@ static int shmem_parse_one(struct fs_context *fc, struct fs_parameter *param)
>   		ctx->huge = result.uint_32;
>   		if (ctx->huge != SHMEM_HUGE_NEVER &&
>   		    !(IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
> -		      has_transparent_hugepage()))
> +		      pgtable_has_pmd_leaves()))
>   			goto unsupported_parameter;
>   		ctx->seen |= SHMEM_SEEN_HUGE;
>   		break;
> @@ -5439,7 +5440,7 @@ void __init shmem_init(void)
>   #endif
>   
>   #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> -	if (has_transparent_hugepage() && shmem_huge > SHMEM_HUGE_DENY)
> +	if (pgtable_has_pmd_leaves() && shmem_huge > SHMEM_HUGE_DENY)

Using pgtable_has_pmd_leaves() here is a bit confusing because the 
definition of pgtable_has_pmd_leaves() is: it returns true if the CPU 
supports PMD-sized pages and false otherwise.

However, tmpfs and shmem already support other sizes of large folios, 
not just PMD-sized large folios.

So, for me, using has_transparent_hugepage() to check would be at least 
clearer (even though it doesn't change the functionality).

Re: [PATCH 07/11] mm: shmem: use pgtable_has_pmd_leaves()

[Luiz Capitulino]

On 2025-12-16 02:52, Baolin Wang wrote:
> 
> 
> On 2025/12/16 05:16, Luiz Capitulino wrote:
>> Shmem uses has_transparent_hugepage() to check if PMD-sized pages are
>> supported, use pgtable_has_pmd_leaves() instead.
>>
>> Signed-off-by: Luiz Capitulino <luizcap@redhat.com>
>> ---
>>   mm/shmem.c | 7 ++++---
>>   1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/mm/shmem.c b/mm/shmem.c
>> index b329b5302c48..ad5825667b49 100644
>> --- a/mm/shmem.c
>> +++ b/mm/shmem.c
>> @@ -689,7 +689,8 @@ static int shmem_parse_huge(const char *str)
>>       else
>>           return -EINVAL;
>> -    if (!has_transparent_hugepage() &&
>> +    if (!(IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
>> +          pgtable_has_pmd_leaves()) &&
>>           huge != SHMEM_HUGE_NEVER && huge != SHMEM_HUGE_DENY)
>>           return -EINVAL;
>> @@ -4655,7 +4656,7 @@ static int shmem_parse_one(struct fs_context *fc, struct fs_parameter *param)
>>           ctx->huge = result.uint_32;
>>           if (ctx->huge != SHMEM_HUGE_NEVER &&
>>               !(IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
>> -              has_transparent_hugepage()))
>> +              pgtable_has_pmd_leaves()))
>>               goto unsupported_parameter;
>>           ctx->seen |= SHMEM_SEEN_HUGE;
>>           break;
>> @@ -5439,7 +5440,7 @@ void __init shmem_init(void)
>>   #endif
>>   #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>> -    if (has_transparent_hugepage() && shmem_huge > SHMEM_HUGE_DENY)
>> +    if (pgtable_has_pmd_leaves() && shmem_huge > SHMEM_HUGE_DENY)
> 
> Using pgtable_has_pmd_leaves() here is a bit confusing because the definition of pgtable_has_pmd_leaves() is: it returns true if the CPU supports PMD-sized pages and false otherwise.
> 
> However, tmpfs and shmem already support other sizes of large folios, not just PMD-sized large folios.
> 
> So, for me, using has_transparent_hugepage() to check would be at least clearer (even though it doesn't change the functionality).

This is more of a naming issue, correct?

Would adding something like thp_has_pmd_support() which expands to:

	return IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && pgtable_has_pmd_leaves();

solve it for you? I suggested it in my RFC, but David advised not to do it.

Also, I'm not sure if the comparison with other folio sizes apply, as
PUD and PMD sizes are special.

Re: [PATCH 07/11] mm: shmem: use pgtable_has_pmd_leaves()

[Baolin Wang]

On 2025/12/16 21:47, Luiz Capitulino wrote:
> On 2025-12-16 02:52, Baolin Wang wrote:
>>
>>
>> On 2025/12/16 05:16, Luiz Capitulino wrote:
>>> Shmem uses has_transparent_hugepage() to check if PMD-sized pages are
>>> supported, use pgtable_has_pmd_leaves() instead.
>>>
>>> Signed-off-by: Luiz Capitulino <luizcap@redhat.com>
>>> ---
>>>   mm/shmem.c | 7 ++++---
>>>   1 file changed, 4 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/mm/shmem.c b/mm/shmem.c
>>> index b329b5302c48..ad5825667b49 100644
>>> --- a/mm/shmem.c
>>> +++ b/mm/shmem.c
>>> @@ -689,7 +689,8 @@ static int shmem_parse_huge(const char *str)
>>>       else
>>>           return -EINVAL;
>>> -    if (!has_transparent_hugepage() &&
>>> +    if (!(IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
>>> +          pgtable_has_pmd_leaves()) &&
>>>           huge != SHMEM_HUGE_NEVER && huge != SHMEM_HUGE_DENY)
>>>           return -EINVAL;
>>> @@ -4655,7 +4656,7 @@ static int shmem_parse_one(struct fs_context 
>>> *fc, struct fs_parameter *param)
>>>           ctx->huge = result.uint_32;
>>>           if (ctx->huge != SHMEM_HUGE_NEVER &&
>>>               !(IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
>>> -              has_transparent_hugepage()))
>>> +              pgtable_has_pmd_leaves()))
>>>               goto unsupported_parameter;
>>>           ctx->seen |= SHMEM_SEEN_HUGE;
>>>           break;
>>> @@ -5439,7 +5440,7 @@ void __init shmem_init(void)
>>>   #endif
>>>   #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>>> -    if (has_transparent_hugepage() && shmem_huge > SHMEM_HUGE_DENY)
>>> +    if (pgtable_has_pmd_leaves() && shmem_huge > SHMEM_HUGE_DENY)
>>
>> Using pgtable_has_pmd_leaves() here is a bit confusing because the 
>> definition of pgtable_has_pmd_leaves() is: it returns true if the CPU 
>> supports PMD-sized pages and false otherwise.
>>
>> However, tmpfs and shmem already support other sizes of large folios, 
>> not just PMD-sized large folios.
>>
>> So, for me, using has_transparent_hugepage() to check would be at 
>> least clearer (even though it doesn't change the functionality).
> 
> This is more of a naming issue, correct?

Yes.

> Would adding something like thp_has_pmd_support() which expands to:
> 
>      return IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && 
> pgtable_has_pmd_leaves();
> 
> solve it for you? I suggested it in my RFC, but David advised not to do it.

I agree with David. The thp_has_pmd_support() is not helpful too. What I 
mean is that the term 'pmd' shouldn't be used here. PMD-sized large 
folios aren't any more special than others.

shmem also supports mTHP, and a better approach might be what you did in 
patch 10: even if PMD-sized pages are not supported on an architecture, 
shmem can still use other sizes of mTHP.

> Also, I'm not sure if the comparison with other folio sizes apply, as
> PUD and PMD sizes are special.

Re: [PATCH 07/11] mm: shmem: use pgtable_has_pmd_leaves()

[Luiz Capitulino]

On 2025-12-16 21:03, Baolin Wang wrote:
> 
> 
> On 2025/12/16 21:47, Luiz Capitulino wrote:
>> On 2025-12-16 02:52, Baolin Wang wrote:
>>>
>>>
>>> On 2025/12/16 05:16, Luiz Capitulino wrote:
>>>> Shmem uses has_transparent_hugepage() to check if PMD-sized pages are
>>>> supported, use pgtable_has_pmd_leaves() instead.
>>>>
>>>> Signed-off-by: Luiz Capitulino <luizcap@redhat.com>
>>>> ---
>>>>   mm/shmem.c | 7 ++++---
>>>>   1 file changed, 4 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/mm/shmem.c b/mm/shmem.c
>>>> index b329b5302c48..ad5825667b49 100644
>>>> --- a/mm/shmem.c
>>>> +++ b/mm/shmem.c
>>>> @@ -689,7 +689,8 @@ static int shmem_parse_huge(const char *str)
>>>>       else
>>>>           return -EINVAL;
>>>> -    if (!has_transparent_hugepage() &&
>>>> +    if (!(IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
>>>> +          pgtable_has_pmd_leaves()) &&
>>>>           huge != SHMEM_HUGE_NEVER && huge != SHMEM_HUGE_DENY)
>>>>           return -EINVAL;
>>>> @@ -4655,7 +4656,7 @@ static int shmem_parse_one(struct fs_context *fc, struct fs_parameter *param)
>>>>           ctx->huge = result.uint_32;
>>>>           if (ctx->huge != SHMEM_HUGE_NEVER &&
>>>>               !(IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
>>>> -              has_transparent_hugepage()))
>>>> +              pgtable_has_pmd_leaves()))
>>>>               goto unsupported_parameter;
>>>>           ctx->seen |= SHMEM_SEEN_HUGE;
>>>>           break;
>>>> @@ -5439,7 +5440,7 @@ void __init shmem_init(void)
>>>>   #endif
>>>>   #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>>>> -    if (has_transparent_hugepage() && shmem_huge > SHMEM_HUGE_DENY)
>>>> +    if (pgtable_has_pmd_leaves() && shmem_huge > SHMEM_HUGE_DENY)
>>>
>>> Using pgtable_has_pmd_leaves() here is a bit confusing because the definition of pgtable_has_pmd_leaves() is: it returns true if the CPU supports PMD-sized pages and false otherwise.
>>>
>>> However, tmpfs and shmem already support other sizes of large folios, not just PMD-sized large folios.
>>>
>>> So, for me, using has_transparent_hugepage() to check would be at least clearer (even though it doesn't change the functionality).
>>
>> This is more of a naming issue, correct?
> 
> Yes.
> 
>> Would adding something like thp_has_pmd_support() which expands to:
>>
>>      return IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && pgtable_has_pmd_leaves();
>>
>> solve it for you? I suggested it in my RFC, but David advised not to do it.
> 
> I agree with David. The thp_has_pmd_support() is not helpful too. What I mean is that the term 'pmd' shouldn't be used here. PMD-sized large folios aren't any more special than others.
> 
> shmem also supports mTHP, and a better approach might be what you did in patch 10: even if PMD-sized pages are not supported on an architecture, shmem can still use other sizes of mTHP.

Oh, I get watch you mean now. I'll have to dig a little deeper into the
shmem code but I'll give your suggestion a try. Thanks for your
feedback.

> 
>> Also, I'm not sure if the comparison with other folio sizes apply, as
>> PUD and PMD sizes are special.
>